CISCO breaks DKIM on their ASA/PIX (again)

Posted by Ralf Hildebrandt on 8 December 2011 | 0 Comments

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site which was using Postfix and a CISCO ASA with "smtp protocol
fixup" enabled.
I was able to work around the delivery problems by stripping the DKIM
headers on outgoing mails (as so often).
Some interesting info got out:
I've also discussed these results with local Cisco support and they
confirmed it's a known bug (not published) with DKIM and smtp inspection
engine in latest IOS versions.
This should be fixed in some newer IOS version (8.4(10)) which is not
public yet (latest is 8.4(2)).

Over the last few days I discussed SMTP delivery problems with a czech site which was using Postfix and a CISCO ASA with "smtp protocol fixup" enabled.

I was able to work around the delivery problems by stripping the DKIM headers on outgoing mails (as so often).

Some interesting info got out:

I've also discussed these results with local Cisco support and they confirmed it's a known bug (not published) with DKIM and smtp inspection engine in latest IOS versions.

This should be fixed in some newer IOS version (8.4(10)) which is not public yet (latest is 8.4(2)).

 


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